Production of chlorine dioxide



Feb. 22., 1938. G. P. VINCENT PRODUCTION OF CHLORINE DIOXIDE Filed Aug. 15, 1934 f n n w o e E E m my, m l? JA. e y v mm e 6. m @W cq t Patented Feb. 22, 1938 y Y l I l AUNITED STATES PATENT OFFICE'.

PRODUCTION OF CHLORINE- DIOXIBE` George Paul Vincent, Niagara. Falls, N. Y., assignor to The Mathieson Alkali Works, Inc., yNew York, N. Y., a corporation of )'irginia a Application August 15, 1934, serial No. 739,888 1o claims. (cies-152) This invention relates to improvements in the the' absorption medium by aeration, to recover production of chlorine dioxide. More particu-v the Chlorine dioxide diluted -With al1', by. heating larly, the invention relates to a method for selecthe charged absorberitmedillm Olby 9L COmbnatively separating chlorine dioxide from a'gas mlxtion Of 'heating and aeration. 5 ture including chlorine and chlorine dioxide, such As previously noted, while the aqueous absorp- 5 as gas mixtures produced by reaction between tion medium need be chemically inert With`re' chlorates and acids, spect to chlorine dioxide only, it is preferably According to this invention, chlorine dioxide chemicalli1 inert With respect to both Chlorine is separated from such gas mixtures by selective dioxide end chlorne. The use of such a medium l absorption of the chlorin'e dioxide in an aqueous is advantageous, for example, in that the'Chlolo medium chemically inert with respect to chlorine rine may be more readily recovered, itsjrecovery dioxide. Preferably the aqueous absorption mecost being much less than-in those cases Where dium `is chemically inert with respect to both the chlorine reacts to any substantial extent with chlorine dioxide and chlorine. The absorption is the absorption medium.` Aqueous media cheml with advantage carried out at low temperatures, lcally inert. aS that term iS used herein, vwith re- 15 between about 10 C. and the temperature at spect to both chlorine dioxide andchlorine in- Whioh the aqueous medium freezes. It may, howclude water, aqueous solutions or mixtures of the ever, be carried out at higher temperatures. BY chlorides and ClllOTateS'O Sodium, Calcium and the use of the low temperatures, the volume of magnesum, andaqueous 'sulfuric acid, advanta- 29 aqueous medium to be handled'is reduced. While geOl-lSlY 0f a cneentiation approximating 40%- 20 the use oi a low temperature reduces the volume 96% H2SO4. of aqueous medium to be handled and results in vIn carrying out the invention. the aqueous abdecreasing the cost of circulation and absorption, Sorpton medium iS With advantagel maintained Whether or not a low temperature should be used in CyClie CirCUletiOn from?. Stripping ZOIle t0 and es in making the separation will depend on whether through an absorption zone and back tothe stripthe savings which can be effected by the use of ping Zone, the sas mixture including chlorine andv alow temperature will be offset by the cost of Chlorine dioxide being COIiteCted illth the absorpproducing the -low temperature. In practical option medium in the absorptifn Z ne and the aberation, therefore, the exact temperature to be SolloeflY chlorine di ide beim st. ipped flOm the :zo used will depend on local conditions in regard to absorption medium 1n the strlppin r Zone.

power, iuel and labor. The invention will be further illustrated by the The aqueous media useful in carrying out the following examples of operations embodying the invention include water, aqueous solutions of inventiom. n Y salts chemically inert with respect to chlorine.v EIGmPle 1--A gas mXtllI'e Consisting 0f apdioxide or mixtures of such salts, such as the prOXmately 'equal PI'OPOI'tOnS of Chlorine and 35 chlorides and chlorates ofA sodium, calcium and chlorine dioxide diluted Withair to an'extent magnesium, and aqueous 'sulfuric acid, advantasuch that the partial pressure of the chlorine rgeously of a concentration approximating 40%' vdioxide approximated 200 mm. of mercury (at 96% HzSOi. While effective separations can be standard conditions) `was scrubbed with water 40 obtained using `Water as the absorption meduim, jat a temperature just above 0 C. 92% of the 40 solutions of salts chemically inert with respect chlorine dioxide originally present but only 14% to chlorine dioxide appear to be particularly adof the chlorine originally present 'were absorbed vantageous. Effective separations can be obby the water, the eilluent gas mixture including tained using aqueous sulfuric acid' as the absorp- 86% of the chlorine and only 8% ,of the chlorine tion medium but recovery'of the absorbed chlodioxide originally present. 45 rine dioxide from water or salt solutions is ef- Example 2.--"I'heA same gasv mixture was fected with greater ease. Completeness of sepscrubbed with 'an aqueous solution of sodium aration o f the chlorine dioxide from such gas chloride containing 26% (by weight) NaCl at a l mixtures is promoted by carrying out the abtemperature of 0 C. 32l parts (byvweight) of sorption .under conditions such, that the partial chlorine dioxidewerea sorbed by thesaline ab- 50 pressure of the chlorine dioxide approximates sorption medium forY every part of chlorine ab- Y 10-500 mm. of mercury or better 50-350 mm. of sorbed. Y mercury in the gas mixture as supplied to the Example 3.*-The same gas mixture was absorption zone. Following absorption, the abscrubbed with aqueous sulfuric acid containingi sorbed chlorine dioxide can be recovered from as supplied to the scrubbing operation, 76% 55 H2504 at a temperature of 3 C. 98% of the chlorine dioxide and substantially none of the chlorine originally present were absorbed by the absorption medium. y

' 5 Example 4.-A gas mixture consisting of approximately equal proportions of chlorine and chlorine dioxide diluted with air to an extent that the partial pressure of. the chlorine dioxidel ap- ,fproximated 35mm. of mercury (at standard conditions) was scrubbed with an aqueous solution oi sodium chlorldecontainlng 26% (by weight) NaCl at a temperature of 24 C. The aqueous solution of'sodium chloride containing absorbed chlorine@ dioxide was subjected to aeration yand chlorine v dioxide 93.9% pure with'v respect to chlorine obtainecb Ii the gas mixture be cooled to about" 3 C. before scrubbing with the laqueous salt solu'- tion and the resultant solution be heated, `by means of steamor hot water, for example, to a temperature of 50C. or 60 C. immediately prior to the strippingoperation a greater yield of. chlo` rine dioxide per unit of timecan be obtainedthan Awhere the operation is conducted as above.

'The accompanying drawing illustrates, diagrammatically and conventionally, forms of ap paratus appropriate for lcarrying out the invention. The apparatus illustrated in Figure 1 providesfor recovery of absorbed chlorine. dioxide by aeration of the absorption mediumand the apparatusillustrated in Figure 2 providesfor.

recovery of the absorbed .chlorine dioxide b y a combination of heating and aeration of the-absorption medium.'

Referring to Figure 1; the tower 3 isthe -abvsorption zone and the tower A4 is -the stripping zone. 'I'hese two towers'xnay be of any convential type' promoting gas and liquid contact, for

,example they Ymay be packed Awith distributing Yelements or they may be of so-called ."bubble. 40 tower construction.

k Y A, through connections I and 6 by means of pump 1.

4dioxide and diluting air for example, is supplied to tower 3 through connection 8.' I'he gasvmixture'remaining after absorption Yot chlorine dlabsorbed chlorine dioxide is conveyed from tower 3 to tower 4 through connection I 0. In tower 4 the charged absorption medium is stripped of absorbed chlorine dioxide by air supplied through connection II. The recovered chlorine dioxide, i s in a mixture with the'air supplied for aeration, is 55 discharged fromtow'er 4 through connection I2.

' Referring to Figure 2,' the same or correspondcharactersv used in Figure 1 withv the letter a of pump Iais cooled, before entering the tower 3a, by passage successively through the heat exchangers I3 and I4. The absorption medium charged with chlorine dioxide flowing from tower y through the heat exchangers `4I3 and I5. In the heat exchanger I3 the charged 'absorption medium is heated and the'stripped absorption medium is cooled by heat exchange between the 70 two. A refrigerating'medium, chilled brine for example, is supplied to heat exchanger I5 through connection I 1.

75 Iclaim: 4

The stripped absorptionmedium from Vtower 4 is supplied to tower 3.

'I'he gasmixture, including chlorine and chlorine oxide in tower 3 is discharged throughy connecf tion 9. The absorption medium vcharged with ing parts are designated by the samereference.

appended. iThe stripped absorption medium sup- 50 plied from. the tower 4a to the tower 3a by means 3a to tower4a is heatedv by passage Asuccessively Y example, is supplied to heat exchanger I4 through connection I6 and a heating medium, steam for 1. In the vproduction of chlorine dioxide,vthe improvement which comprises separatingchlorine dioxide from a gas mixture including chlorine and chlorine dioxide by selective absorption of the chlorine dioxide in aqueous sulfuric acid, and recovering chlorine dioxide from the absorption medium.

ain the production of chlorine dioxide, the

improvement which comprises separating chlorine dioxide from a gas mixture including chlorine and chlorine dioxide by selective absorption `of the chlorine dioxide in aqueous sulfuric acid at a temperature below about 10 C., and recovering chlorine dioxide from the absorption medium.

3. In the 'production of chlorine dioxide, the improvement'` which comprises separating chlorine dioxide `from a gas mixture including chlorine and chlorine dioxide by selective absorption of the chlorine dioxide in an aqueous solution containing' a chloride and a chlorate of one or more elements of the group consisting of sodium,

calcium and magnesium, and recovering chlorine 1 dioxide from the absorption solution. 1

4. InV the production of chlorine dioxide, the

improvement which comprises separating tchlo-v rine dioxidefrom a gas mixture including chlorine and chlorine dioxide by selective absorption of the chlorine dioxide in an aqueous solution containing a chloride of an element ofthe group consisting of sodium, ,calcium andv magnesium,

'and recovering chlorine dioxide from the absorp- 5. In the production oi chlorine dioxide. the

improvement which comprises separating chlorine dioxide from a gas mixture including chlorine and chlorine dioxideby selective absorption'of the chlorine dioxide in an aqueous solution' containingachlorate of an element of the group con- .sisting of` sodium, calciumgand magnesium, and I recovering chlorine dioxide from the absorption solution.

afin the' production of ohiorine dioxide, ooeA improvement which comprises separatingchlorine dioxide from a gas mixture including chlorine and chlorine dioxide by selective absorption ofthe chlorine dioxide in anaqueous' solution containing a chloride and a c hlor'ate of one o r more elements of the group consisting of sodium, calcium and magnesium ata temperature below about 10 C., and recovering chlorine dioxide from the absorption solution. I'

'7. In the production of chlorine dioxide, the

improvement which comprises separating -chlorine dioxide from a gas mixturex-including chlorine and chlorine dioxide by'selective absorption of the chlorine dioxideinf an aqueous solutionV `containing a chloride of an element of the group consisting of sodium, calciuinand magnesium at a temperature below about l0"v C., and recovering chlorine dioxide from the absorption solution.

8. In'the production of chlorine dioxide, the improvement whichv comprises separating chlorine dioxide from a gas mixture including chlorine and chlorine dioxideby selective absorption ,a salt of one or more elements of the group consisting of sodium, calcium and magnesium, which salt is chemically inert with respect to chlorine dioxide and chlorine, and recovering chlorine dioxide from the absorption solution.

l0. In the production of chlorine dioxide, the improvement which comprises separating chlorine dioxide from a gas mixture including chlorine and chlorine dioxide by selective absorption of the chlorine dioxide in an aqueous solution containing a material chemically inert with respcct to chlorine and chlorine dioxide of the class consisting of sulphuric acid and salts of the elements of the group consisting of'sodium, calcium and magnesium, and recovering chlorine dioxide from the absorption solution.

GEORGE PAUL-VINCENT.. 

